The present invention relates generally to a magnetic tape cassette case, and more particularly to a case for receiving a magnetic tape cassette with an index card disposed therebetween, wherein the case or index card where air entrapped in the pocket-shaped portion of the case is vented when the cassette and index card are inserted therein.
An audio or video magnetic tape cassette (hereinafter referred to simply as a cassette) when in an inoperative state is typically stored in a magnetic tape cassette case (hereinafter referred to simply as a case). The case is used primarily for protecting the cassette from damage due to external forces and for preventing dust from entering the interior of the cassette. In recent years, the performance of magnetic tape cassettes and recording/reproducing apparatus have improved such that even a minute amount of dust clinging to a magnetic tape is likely to cause problems such as signal dropout. Therefore, it is very important to prevent dust from entering the cassette.
Magnetic tape cassette cases, most of which are made of plastic, include an inner housing portion having a pocket into which the cassette is inserted, and an outer housing portion pivotally coupled to the inner housing portion so that they can be closed and opened to and from each other. Other cases are made of a resin sheet punched out to a prescribed form, bent, and conjoined to itself with an adhesive so as to be shaped like a book container.
To visually indicate or identify items recorded on a magnetic tape, the conventional case described above is provided with an index sheet 11 which allows such items to be written thereon, as shown in FIG. 1. In FIG. 1, a conventional case is known and will now be described in more detail.
The case 30 includes a cover 2 having a pocket 4, and a casing portion 8 represented by phantom lines pivotally coupled to the cover 2. The casing portion 8 rotates about a support shaft (not shown), which is pivotally fitted into shaft holes 7a, to open and close the case. The index sheet 11, which fits into the pocket 4 of the cover 2, is formed by folding it along folding lines 12 and 13 at the right-hand end part thereof, forming a U-shaped sectional contour. The folded part 15 of the index sheet 11 is inserted into the pocket 4 of the cover 2, and then desired identification marks such as the title of the recorded contents can be written onto the surface of an upright wall 13a at the folded part 15 of the index sheet 11. The written marks can visually be read through a transparent rear surface wall 6 of the case 30.
Since the open front part of the magnetic tape cassette is covered with the bent portion of the index sheet, the cassette is better protected from damage due to external forces.
The index sheet 11, which is folded along the folding lines 12 and 13 in the U-shaped configuration, is dimensioned such that a height l.sub.2 of the upright wall 13a as measured in the direction of a thickness of the cassette is substantially equal to the height L.sub.2 of the pocket 4 as measured in the direction of a thickness of the pocket 4. The height l.sub.1 of the folded part 15 of the index sheet 11 at the forwardmost end of the same is larger than the height L.sub.2 of the pocket 4. With such construction, when the index sheet 1 is inserted into the pocket 4, it is firmly held in the pocket 4 with the aid of the elastic force of the folded part 15 of the index sheet 11, which expands outwardly. Thus, the index sheet 11 will not fall out of the pocket 4, even if no cassette is in the case 30. In addition, since the folded part 15 of the index sheet 11 elastically contacts a small wall surface 5 of the pocket 4, a cassette will not collide with the folded part 15 of the index sheet 11 when it is inserted into the pocket 4 of the case 30.
However, the conventional case constructed in the above-described manner, has the following disadvantages. That is, the index sheet 11 receives a large resistance when it is inserted into the pocket 4 on a mass production line, resulting in an inefficient insertion operation. Particularly, when the index sheet 11 is inserted into the pocket 4 at high speed with automatic equipment, it receives a larger resistance due to the compression of air than from a frictional resistance because air is entrapped in the space between the pocket 4 and upright wall 13a of the index sheet 11 and cannot be vented to the outside. This further causes the index sheet 11 to be bent as it is inserted in the pocket 4. Thus, there arises another problem associated with the conventional case on a mass production line, namely, the inserting operation can bend the index sheet.